1. Field of the Invention
The invention relates generally to external lighting for aircraft and more particularly to an LED aviation warning light incorporating redundancy and fault detection features.
2. Description of the Related Art
Civilian air traffic control agencies such as the FAA specify standards for aircraft external lighting. Aircraft operating at night in civilian airspace are required to display lights to attract the attention of other aircraft operating in the same airspace. These external aircraft lights include flashing anti-collision lights mounted on the aircraft's upper and lower fuselage, as well as position/navigation lights on the tail and the wing tips. The location, color, intensity and light radiation pattern for each particular light is typically specified by the relevant regulation.
Aircraft external lighting have previously been provided by “strobe” lights or incandescent lamps. Incandescent and strobe lamps suffer from relatively high power consumption and relatively short service life.
With advances in the efficiency of light output from light emitting diodes (LEDs), it is now possible to replace incandescent and strobe lamps with LED light sources. LED light sources are attractive because of their extremely long service life and relatively low power consumption. High-output LEDs, such as the Luxeon™ emitter from LUMILEDS™ of San Jose, Calif., in certain configurations can achieve the required light output and radiation pattern for an aircraft position light.
Strobe and incandescent light sources typically employ a single light source, making failure of that light source readily apparent upon inspection. An LED light source may employ multiple LED light sources due to the relatively low quantity of light produced by each LED. If all of the LEDs are arranged in series, failure of any individual LED would extinguish the entire light. Alternatively, subsets of LEDs could be arranged in a series/parallel configuration such that failure of any one LED would extinguish only the LEDs in that series branch, with the remaining LEDs continuing to operate. This type of redundancy prevents total failure of the light assembly. However, partial failure of an aircraft warning light may result in a light that fails to meet the requirements of the relevant regulation, while appearing to function normally to the typical observer/inspector. There is a need in the art for an LED aviation warning light configured to continue to function after failure of one or more LEDs that is also configured to detect failure of the LED light sources and provide some indication of that failure.